1. Technical Field
The present invention relates to a method for synthesizing a modified polymer comprising epoxide groups along the polymer chain. More particularly, the present invention relates to obtaining these epoxidized polymers by functionalization of an unsaturated diene polymer. The invention also relates to the functional polymer obtained and the crosslinkable composition containing same.
2. Related Art
Polymers bearing epoxide functions are widely used in various applications for the reactivity of the epoxide function. They are mainly used in those fields of industry calling for elastomers having to be crosslinked in a way other than via sulphur.
The epoxide function may be borne directly by the carbon backbone of the diene polymer, and is then mainly obtained by epoxidation of the carbon-carbon double bonds initially present after copolymerization. This epoxidation of unsaturated polymers is well known to those skilled in the art and may be carried out for example by methods based on chlorohydrin or bromohydrin, methods for direct oxidation or methods based on hydrogen peroxide, alkyl hydroperoxides or peracids (such as peracetic acid or performic acid).
The epoxide function may also be pendant and is then already present in a monomer involved in the copolymerization with the other monomer(s) making up the polymer (this monomer may, for example, be glycidyl methacrylate, allyl glycidyl ether or vinyl glycidyl ether).
The use of a monomer already comprising the epoxide function for synthesizing the epoxidized polymer necessitates specific copolymerization operating conditions which limit the flexibility of the synthesis method. Indeed, some syntheses require very high pressures for gas phase radical copolymerizations of copolymers based on glycidyl methacrylate, for example terpolymers of ethylene, vinyl acetate and glycidyl (meth)acrylate (commercial products LOTADER AX8840® and AX8900® and Arkema patent EP0599684A1). Moreover, it is known to those skilled in the art that polar functions, such as glycidyl functions, can act as a poison to catalytic complexes used for the coordination-insertion polymerization of monomers.
The technical problem posed in light of the prior art is being able to have a method which enables simple and controlled synthesis of a polymer bearing epoxide functions along the chain, with a level of productivity in keeping with industrial production.
In the pursuit of their research, the inventors have now developed a novel method for synthesizing a polymer bearing pendant epoxide functions along the chain by grafting a hydrosilane bearing an epoxide function onto the unsaturations of the polymer by a hydrosilylation reaction. The grafting yield is high, possibly reaching 100% on the unsaturations. The method according to the invention is simple, reproducible and able to be used on an industrial scale.
Patent applications WO 2003/085024 A1, JP4586966B2, JP2006002035A, JP07133347A and JP05339504A report the use of hydrosilanes for introducing an epoxide function at the chain end of vinyl- or allyl-terminated polymers. Thus, after polymerization, functions at the chain end of polymers are modified by hydrosilylation using epoxide-functional hydrosilanes. In WO 2003/085024 A1, the authors dealt with the functionalization of allyl-terminated polyisobutylene. In documents JP4586966B2 and JP2006002035A, the authors dealt with the functionalization of vinyl-terminated polyimides and fluoropolyethers. In JP07133347A, the authors dealt with the functionalization of vinyl-terminated polysiloxanes. In JP05339504A, the authors dealt with the functionalization of allyl-terminated aromatic polyether. These modifications by hydrosilylation require the polymer to be exclusively non-diene and end-functionalized beforehand by an allyl or vinyl group. Moreover, this does not concern the synthesis of polymers bearing epoxide functions along the chain.